Experimental study on evolution of pore structure of cementitious pastes using different techniques

Hydration of cement results in the formation of pores, which are mostly interconnected. Supplementary cementitious materials (SCM) lead to a reduction in the interconnectivity of the pores, as well as alter the pore size distribution. An assessment of the performance of alternative cements incorporating SCMs should therefore necessarily include a study of the pore structure characteristics. In the recent times, there has been a renewed interest in calcined clay based SCMs for cement concrete, because of the large reserves of such materials. Further, the use of limestone in a ternary combination with cement and calcined clay gives rise to a new chemistry that can be successfully used to produce high quality cementing materials for concrete. The work reported in this paper is part of a larger project that investigates the potential for limestone – calcined clay based cementitious binders in concrete. This paper describes an experimental investigation of the pore structure of different binder systems using mercury intrusion porosimetry and electrical conductivity measurements. The parameters investigated include total porosity, pore size distribution, and threshold diameter of pores. The cementitious systems include: (i) ordinary Portland cement (OPC), (ii) Portland pozzolana cement (PPC– i.e. OPC with 30% Fly Ash Type F), (iii) Limestone Calcined Clay Cement (LC3).